part 0 2413 bytes<P><FONT SIZE=2 FACE="Arial">&gt; The trouble with the</FONT>
<BR><FONT SIZE=2 FACE="Arial">&gt; software only approach is that you have to complete all calculations</FONT>
<BR><FONT SIZE=2 FACE="Arial">&gt; and keep a pretty accurate counter in between firing cycles.</FONT>
</P>

<P><FONT SIZE=2 FACE="Arial">Not neccessarily.</FONT>
</P>

<P><FONT SIZE=2 FACE="Arial">The last software I wrote precalculated a set of variables and these are</FONT>
<BR><FONT SIZE=2 FACE="Arial">used at run time - virtually no math while running. The data is then</FONT>
<BR><FONT SIZE=2 FACE="Arial">available exactly when needed. As I mentioned earlier, I can keep track</FONT>
<BR><FONT SIZE=2 FACE="Arial">of RPM, pos or neg advance, vac adv, dwell and rev limit in about 50</FONT>
<BR><FONT SIZE=2 FACE="Arial">instructions. That is about 25uS @ 8MHz, but it still becomes an issue</FONT>
<BR><FONT SIZE=2 FACE="Arial">at high RPM.</FONT>
</P>
</UL>
<P><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">That's pretty good actually.&nbsp; I had a look at your code on your web page a while back and IIRC the program loop took 100us which gave pretty course resolution at higher RPM.&nbsp; I guess you've optimised that a fair bit!</FONT></P>

<P><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">So if I understand you correctly, you don't store a table of advance angle values in degrees, but store a table of time values, avoiding the need to perform angle/time conversions?&nbsp; Did you consider using the compare/capture units of a higher end PIC instead of a purely software solution? What would be nice is to have some way of modifying timing values in real time for setting up on a dyno or rolling road.</FONT></P>

> That's pretty good actually. I had a look at your code on your web
> page a while back and IIRC the program loop took 100us which gave
> pretty course resolution at higher RPM. I guess you've optimised that
> a fair bit!

That was the main reason for using it on "low" performance engines.

I actually had one person ask if it would be OK to use it in his
aircraft. After a quick shudder, a hasty 'no' was the asnswer.

> So if I understand you correctly, you don't store a table of advance
> angle values in degrees, but store a table of time values, avoiding
> the need to perform angle/time conversions?

Yes. Two data sets use up about 40 bytes of EEPROM.

> Did you consider using
> the compare/capture units of a higher end PIC instead of a purely
> software solution? What would be nice is to have some way of modifying
> timing values in real time for setting up on a dyno or rolling road.

At the time I wanted a flash or EEPROM based system. In the PIC world,
the only one available was the C(F)84. The 87X would open up some new
possibillities.

I've been trying to release the code for this project, but a company is
still making a dollar or two from it, so I've been holding back.

Tony Nixon wrote:
> > Michael Rigby-Jones wrote:
> > That's pretty good actually. I had a look at your code on your web
> > page a while back and IIRC the program loop took 100us which gave
> > pretty course resolution at higher RPM. I guess you've optimised that
> > a fair bit!
>
> That was the main reason for using it on "low" performance engines.
>
> I actually had one person ask if it would be OK to use it in his
> aircraft. After a quick shudder, a hasty 'no' was the asnswer.

"No Sense of Adventure", Tony! <G>

How'd they get an aircraft without Magnetos? Experimental aircraft?

I'd guess you could shoehorn something in there (take the mag's points
as inputs, supply powered outputs to the coils, high reliability
battery?) - Bet the FAA would mumble loudly at you when inspected,
though. With dual mags per engine (for good reason!) and the pre-flight
checklist including testing both mags, common sense says that it's a
GOOD thing to keep the engine very very reliable, rather obviously...
Sorta hard to change 2 sets of curves at the same time, synchronized,
with all that reliability, too.

Good answer - Searches for aircraft aren't much fun. Should *this
person* be FLYING, though? Poor judgement is NOT a good indicator of
good flying capability, "there are no old, bold pilots", as you know...

> Good answer - Searches for aircraft aren't much fun. Should *this
> person* be FLYING, though? Poor judgement is NOT a good indicator of
> good flying capability, "there are no old, bold pilots", as you know...
>
> Mark

Part of my bias is that, having done Search flying here in Washington
State, I know how few and far between the good safe landing sites are
when up in the Cascades; It'd be a lot less critical in some states <G>

How to put this... Most pilots have a clue and are good 'n safe. There
are just a few BOZOs, though. Flying's only as safe as it is, because
most people follow the rules and pay attention.

The BOZOs don't check the fuel sumps for water / other fuel
contamination, or run checklists, etc. I almost 'met' one on my first
solo flight - he was in a low-wing plane (Bonanza?) at 700 or so feet
AGL, came out from under the nose of the C172 I was in at 800 feet AGL
(the proper pattern height) in the same pattern, when I lowered the
flaps and the nose came down there he was - We could have had a mid-air
collision easily if I'd descended while on the downwind leg. I went
around, to be safe... He hadn't bothered to look for anyone ELSE in the
pattern (he was faster than I was, came in from behind & under me; he
could have seen me if he'd tried to look!), he hadn't bothered to come
up on the field frequency and announce himself, or to listen to my
announcements on that field frequency, either - He didn't belong in the
air, IMO. My CFI (certified flight instructor) "took care" of him, I
understand - Wish I'd heard what my CFI said, ALMOST... Imagine it was
"colorful, loud, and quite effective" - rightly so.

The BOZOs do things like flying 60 feet off the ground, at 60+ degree
bank angles, inside the pattern, just to "show off", in a perfectly good
Bird Dog (Beautiful plane, quite dangerous pilot, who wasn't as
competent as he hallucinated.) (Engine failure or judgement lapse in
that situation = a crash, most likely.)

I participated, back in my Search and Rescue days, in quite a number of
searches where the low-hours VFR pilot was (literally!) told, asked, or
even BEGGED by the Fixed Base Operator (usually a pilot and usually a
pretty knowledgeable person about weather etc.), NOT to go flying that
day (bad IFR weather) - some lied and said they "were just topping the
tanks up", some didn't lie, all of them flew anyways, and didn't make
it. That's darn POOR judgement IMO. Myself, I'm not happy with flying
as an observer in near-IFR weather, even with the best of pilots,
looking for someone who typically died in the crash; that isn't MY idea
of fun, at all; Only went up to try to save a life. (There're GOOD
reasons that the average lifespan of VFR pilots flying in IFR
conditions, is something like 90 seconds (last I heard) - until you get
the RIGHT training, and unless you USE that training competently, IFR is
dangerous. A few do make it - so, obviously, some don't last near 90
seconds. About as safe as "Russian Roulette"...)

The BOZOs also do things like a CFI who pancaked an aircraft in on a
mountain ridge while showing a student pilot "how to mountain fly", then
didn't "deign" to notify the NTSB, to avoid the consequences (they
carried the engine & many parts out, but didn't clean up the window
shards; A civilian pilot saw the glitter during a search, called it in
to us as a possible lead (Good guy!), we got an N number off the pieces
of plane left there, and traced the plane. That CFI's possibly still
suspended.)

Think of someone with THAT sort of level of judgement, who thinks they
can ignore both the laws AND the intent of the laws, who decides to
solder a copy of Tony's circuit together (with Acid Core solder,
probably, using wire nuts sans electrical tape to put the untested
package onto their aircraft's ignition system), then thinking they're
immortal and flying it, that's rather obviously not flying wisely...

Definitely, I'd bet most of us on this list and most pilots, would do
better than THAT <G>; What I was alluding to is that, "if you have to
ask Tony if you can do it, maybe you'd better NOT, until you know for
darn certain that you CAN safely do it. Then talk with TOny about it."

My impression from Tony's post was that he didn't think that his circuit
/ software, was ready for flight-critical use at all - Look into what it
takes to test things to flight-critical status, if you don't already
know - they get quite stringently tested, lots of test hours, lots of
expense. Any of us could test such hardware/software, it's a LOT of
work and effort though. Probably a lot easier to put such on a
Sport/Experimental aircraft than a general aviation A/C...

I'd bet a LOT that STC has reams of documents that the FAA's reviewed
(as do Slick and Bendix) to check the safety of those systems - Testing
on a GroundProx system is pretty thorough, I know from doing it; If
Tony's system fails on a car, he'd pull over, park, and fix it - He
doesn't need a Skyhook, unlike when flying a light aircraft.

> Part of my bias is that, having done Search flying here in Washington
> State, I know how few and far between the good safe landing sites are
> when up in the Cascades; It'd be a lot less critical in some states <G>

Many years ago, I did search & rescue flying in the Mississippi delta on and off
for about 17 years, mostly in a J-3. We have a LOT more landing sites than you
do. In fact, at typical cruising altitude, we are generally within gliding range
of at least 2 airports, sometimes more. Even so, I still have more landings and
takeoffs off-airport than I do on. We were usually looking for floaters rather
than downed pilots. Re mods for general aviation, I am a strong believer in the
STC process and have one under review by the FAA at the moment, with more in the
mill. My point is that these STC'd systems are not that undependable. But it
sounds like you're more bothered by goofy pilots than by the hardware problem.
Luckily, I've not run into as many goofs as you have.

> My impression from Tony's post was that he didn't think that his circuit
> / software, was ready for flight-critical use at all - Look into what it
> takes to test things to flight-critical status, if you don't already
> know -

I know. Don't really agree with you about the average difficulty though.

> Probably a lot easier to put such on a
> Sport/Experimental aircraft than a general aviation A/C...

Much easier, but not impossible. Or you can simply put the GA craft into
experimental category for test purposes. One of my friends has done just that,
making it far easier to do flight testing. Even then, the paper work is noticible,
but not monumental.

> I'd bet a LOT that STC has reams of documents that the FAA's reviewed
> (as do Slick and Bendix) to check the safety of those systems - Testing
> on a GroundProx system is pretty thorough, I know from doing it; If
> Tony's system fails on a car, he'd pull over, park, and fix it - He
> doesn't need a Skyhook, unlike when flying a light aircraft.

Well, actually around here, if you have an engine failure you just land the plane,
walk to a road, hitchhike to a phone, and if there's no damage, call someone to
come fix the sucker and log it (helps if you notify the FAA and the sheriff too,
but isn't required if neither the plane nor any people or property are damaged).
There's something to be said for living in flat, open states. But engines don't
quit all that often. It's happened to me only twice in 35 years. As an aside, in
J-3's the fuel gage is a wire running through a hole in the gas cap that sits on
the cowl boot in front of the windshield. The wire has a hook on the top and a
cork on the bottom and the amount of fuel remaining is indicated by how far the
hook is sticking up in the air. That little wire is a world-class dew collector,
running it right down into the fuel tank. So with a cub, first flight of the
morning you drain the sump, pick the tail up above your head, shake it (the tail,
not your head), set it down, and drain the sump again. If you're paranoid (I am)
you do that a couple of times.

My RC plane instructor is an old J-3 pilot. I LOVE the whole concept of
being able to pick up the tail section all by yourself and shaking it :-)
My Dad (also a J-3 nut) refers to the Cub as "the minimal airplane". <G>

Sean

At 08:21 PM 5/4/00 -0700, you wrote:
>running it right down into the fuel tank. So with a cub, first flight of the
>morning you drain the sump, pick the tail up above your head, shake it
(the tail,
>not your head), set it down, and drain the sump again. If you're paranoid
(I am)
>you do that a couple of times.
>
|
| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
Save lives, please look at http://www.all.org
Personal page: http://www.people.cornell.edu/pages/shb7.....shb7KILLspam@spam@cornell.edu ICQ #: 3329174

James R. Cunningham wrote:
> Mark Willis wrote:
> > Part of my bias is that, having done Search flying here in Washington
> > State, I know how few and far between the good safe landing sites are
> > when up in the Cascades; It'd be a lot less critical in some states <G>
>
> Many years ago, I did search & rescue flying in the Mississippi delta on and off
> for about 17 years, mostly in a J-3. We have a LOT more landing sites than you
> do. In fact, at typical cruising altitude, we are generally within gliding range
> of at least 2 airports, sometimes more. Even so, I still have more landings and
> takeoffs off-airport than I do on. We were usually looking for floaters rather
> than downed pilots. Re mods for general aviation, I am a strong believer in the
> STC process and have one under review by the FAA at the moment, with more in the
> mill. My point is that these STC'd systems are not that undependable. But it
> sounds like you're more bothered by goofy pilots than by the hardware problem.
> Luckily, I've not run into as many goofs as you have.

Good! <G> "Get-There-Itis" is a bad disease for pilots to get.

Around here, I think of proper cruise altitude as about 10,500 feet MSL
or so - Gives you some glide range, and not too many rocks at THAT
altitude around here. Far smarter than the "I Fly Roads" method of
flying in low-visibility weather.

There've been a lot of crashes (~100) around Alpental (near Snoqualmie
Summit), for example - people fly up the road, mistake the lights at
Alpental as being on I-90, and are in the box canyon there before they
know it, unable to turn safely. Pretty eye-opening, to a beginning
pilot. Another "favorite" problem's trying to "thread the needle" (fly
through a notch in a long mountain range in SWestern WA), a BAD idea.
(I'd have to look up the name of that pass.) Best way to fly mountains
IMO is at a nice decent altitude OVER 'em, unless you've taken some
serious training.

> > My impression from Tony's post was that he didn't think that his circuit
> > / software, was ready for flight-critical use at all - Look into what it
> > takes to test things to flight-critical status, if you don't already
> > know -
>
> I know. Don't really agree with you about the average difficulty though.

It's probably quite a lot easier to certify stuff for General Aviation
A/C than for Commercial A/C (It's BAD if someone crashes a C172 with 3
on board - lots worse if a 747-class airplane with 100+, though. They
might have tougher requirements. Box I worked on had an Z80 for A/D
conversions, 80186 for digital filtering; They made a different but
quite similar model for newer commercial A/C.)

> > Probably a lot easier to put such on a
> > Sport/Experimental aircraft than a general aviation A/C...
>
> Much easier, but not impossible. Or you can simply put the GA craft into
> experimental category for test purposes. One of my friends has done just that,
> making it far easier to do flight testing. Even then, the paper work is noticible,
> but not monumental.

Makes sense. WANT to get back flying, some day... May well be an
Experimental.

> > I'd bet a LOT that STC has reams of documents that the FAA's reviewed
> > (as do Slick and Bendix) to check the safety of those systems - Testing
> > on a GroundProx system is pretty thorough, I know from doing it; If
> > Tony's system fails on a car, he'd pull over, park, and fix it - He
> > doesn't need a Skyhook, unlike when flying a light aircraft.
>
> Well, actually around here, if you have an engine failure you just land the plane,
> walk to a road, hitchhike to a phone, and if there's no damage, call someone to
> come fix the sucker and log it (helps if you notify the FAA and the sheriff too,
> but isn't required if neither the plane nor any people or property are damaged).
> There's something to be said for living in flat, open states. But engines don't
> quit all that often. It's happened to me only twice in 35 years.

That's Lots safer than in the Cascades. More than once on a search,
I've looked over the landscape while in our grid - with an engine
failure, we'd be ON the ground, too soon. It's UP to all ridges, in all
directions, and a pretty twisty turny way downstream - and a C172's
glide ratio isn't all THAT good... Nice snow pack on the ground, even
with a nice survival kit in the back, STILL "let's not and say we
didn't." Haven't quite been at so low a level that we brought home
foliage in the landing gear, close enough though.

> As an aside, in
> J-3's the fuel gage is a wire running through a hole in the gas cap that sits on
> the cowl boot in front of the windshield. The wire has a hook on the top and a
> cork on the bottom and the amount of fuel remaining is indicated by how far the
> hook is sticking up in the air. That little wire is a world-class dew collector,
> running it right down into the fuel tank. So with a cub, first flight of the
> morning you drain the sump, pick the tail up above your head, shake it (the tail,
> not your head), set it down, and drain the sump again. If you're paranoid (I am)
> you do that a couple of times.

'Paranoia' is a good pilot's survival skill, really. Consequences in 90
seconds for a serious screw-up, means intelligent caution's a GOOD idea,
to me <F>

Because you're 'paranoid', you're likely to live longer, in that fuel
sump waterlogging situation. That's probably quite a fun plane to fly,
too. "So many planes, so little fuel money"!